1. Field of the Invention
The present invention relates to a drum lug structure, and in particular relates to a drum lug structure capable of imparting a prescribed tension to the drum head.
Priority is claimed on Japanese Patent Application No. 2008-001084, filed Jan. 8, 2008, the content of which is incorporated herein by reference.
2. Description of the Related Art
Drum lug structures of various drums such as shown for example in FIG. 7, FIG. 8A and FIG. 8B are known in which lugs are used in order to provide, in a tensioned state, the drum head over the drum shell, with a rim or similar intervening (see Japanese Patent Publication No. 3707485 [Japanese Unexamined Patent Application, First Publication No. 2004-151701]).
In FIG. 7, the upper portion of a lug 50 holds a tightening bolt 51, and the lug 50 is installed on the drum shell 53 via a pin-shape lug base 52. In the lug base 52 is formed a V-shape engagement groove 52A along the circumferential direction of the pin. On the other hand, an angled protrusion 50A is provided on the lug 50. By engaging the engagement groove 52A and the protrusion 50A, the lug 60 is installed on the lug base 52.
A lug 60 shown in FIG. 8A and FIG. 8B is fixed to the drum shell, not shown. This lug 60 has a shape having a receiving groove 63 which receives a cylindrical lug nut 62, which screws onto the tightening bolt 61.
However, in the structure of FIG. 7, even when the engagement groove 52A and the protrusion 50A are engaged, it is difficult to restrain rotational movement by the lug 50 in the circumferential direction (the direction of the arrows R in the figure) of the lug base 52. This gives rise to a difficulty in which, after installing the lug 50 on the lug base 52, the lug 50 readily becomes an inclined state in the direction of the arrows R.
Further, in the structure of FIG. 8A and FIG. 8B, the receiving groove 63 has a depressed shape along a semicircular column. Hence as shown in FIG. 8B, in a side view the portion of contact between the cylindrical lug nut 62 and the receiving groove 63 is a single point P, and so there is the difficulty that the lug nut 62 is easily shifted in the left or right directions in the figure.
Further, when the tightening bolt 51 is loosened, in the structure shown in FIG. 7, the engagement of the engagement groove 52A and the protrusion 50A is released. When the tightening bolt 61 is loosened, in the structure shown in FIG. 8A and FIG. 8B the lug nut 63 drops downward from the receiving groove 63 in a free state. As a result, when in a state of preparation to install the rim and similar, the lug 50 in FIG. 7 and the lug nut 63 in FIG. 8 move easily, and so must be held by hand, and for this and other reasons, there is the difficulty that working conditions are worsened.
It is known that by changing the total mass of the lugs and lug bases, the tone of the drum can be changed; and it is desirable that the tone be easily adjustable.